1. Field of the Invention
This invention relates to power splitters in general and more particularly to a power splitter having a small package size.
2. Description of Related Art
Power splitters have been made by forming transmission lines on microstrip structures using printed circuit boards. Power splitters have also been fabricated on ceramic substrates using screened on thick film conductors and dielectrics. In some applications, printed circuit board space is extremely limited with additional space just not available. It is desirable that the splitter be as small as possible while still having the proper impedance and not having excessive cross-talk noise. Printed circuit boards have a problem in power splitter applications in that the desired transmission line impedance can be hard to achieve in a small package size due to the low dielectric constant of the printed circuit board material. Ceramic materials have a higher dielectric constant and can achieve the same impedance transmission lines in a smaller size. Unfortunately, using a thick film process to fabricate a multilayered structure is difficult to manufacture on a repeatable and cost effective basis. Further, if the circuit lines are placed to close to each other in the ceramic package, excessive cross-talk noise can result.
Power splitters have also been made using balun transformers. The transformer is difficult to repeatedly produce. Variations in tightness of the windings, magnet wire twist rate and permeability/permissivity of the ferrite material cause the transformer electrical parameters to shift and vary. Transformers are large and require excessive amounts of space on a printed circuit board. Transformers are difficult to assemble to a circuit board requiring a lengthy manual assembly process by a skilled operator. This adds undesirable cost to the product and is difficult for large scale manufacturing.
While power splitters have been used, they have suffered from taking up excessive space, being difficult to manufacture and expensive. A current unmet need exists for a power splitter that is smaller with good electrical performance, that can be repeatably manufactured and that is low in cost.